The invention relates to pressure cookers comprising a pan and a lid fitted with a gasket to provide sealing between the lid and the pan when the pressure cooker is under pressure.
Pressure cookers having an annular sealing gasket made of a deformable material for the purpose of providing sealing between a pan and a lid are known.
The safety aspects of pressure-cooker operation are also well known. High pressure exists inside the appliance during cooking and excess pressure is potentially dangerous. To improve the safety systems on pressure cookers, various safety devices that are activated simultaneously or in succession in the event that a maximum operating pressure is exceeded have been used. It is well known to provide pressure cookers with one or more safety devices including one or more safety valves coexisting with a safety device that relies on deforming the sealing gasket.
It is also known to use a sealing gasket that is extruded through an opening in the side wall of the lid in the event of excess pressure. The gasket moves outwardly as it extrudes through the opening. As the gasket is extruded, the bottom lip of the gasket moves downwardly beyond its sealing position, so that fluid escapes downwardly along the walls of the pan of the pressure cooker. Although such a device provides the pressure cooker with additional safety, it suffers from disadvantages. The lid must be formed with an opening during manufacture. In addition, the sudden escape of fluid down the sides of the appliance can extinguish the heater element and cause a safety problem. A scalding fluid is squirted from the pressure cooker under pressure and may be squirted onto the user.
To improve such a device, and in particular to diminish the violent effects of the gasket being extruded, gaskets with special shapes have been envisioned. The gasket extrusion window in the lid is eliminated, and a series of notches around the entire inner and outer periphery of the annular gasket are formed. The notches are associated in pairs with internal nicks. In operation, in the event of excess pressure, the gasket deforms radially at one or more notch/nick pairs, causing the fluid to escape progressively towards the bottom of the appliance. Such a device ensures that the fluid leaks in relatively progressive manner towards the outside. However, the manufacture of the annular gasket is complicated by the multiplicity of shapes to be provided. Leaks may occur in normal operation. Numerous notch/nick pairs around the periphery of the gasket are required to ensure that there is at least one notch/nick pair that is operational when the gasket is in place between the ramps on the pan and the lid. The ramps on the pan can interfere with downward displacement of the lips of the gasket over certain annular sectors.
To attempt to solve the above-mentioned problems, the gasket is provided on its periphery with two radial tongues. The radial tongues are arranged to be inserted in an opening formed in the peripheral side edge of the lid to index rotation of the gasket with rotation of the lid. The gasket has a notch in its inner periphery geometrically associated with indexing nicks to ensure that the gasket is extruded through the opening.
Such a safety device nevertheless suffers from the drawback of requiring an extrusion opening to be made in the lid. Furthermore, the above-mentioned drawbacks concerning extrusion of the gasket remain. Such a device does not prevent mounting a standard gasket in the lid of the pressure cooker. A gasket which is not specially designed to be fitted to such a pressure cooker, having no indexing nicks, may be used with the pressure cooker. Such incorrect operation of the appliance degrades its safety in use.
Another example of an indexed gasket is described in detail by German Patent No. 1076922, which proposes two studs in the lid arranged to be inserted in two openings in the gasket so as to index the position of the lid. As in all known embodiments of indexing gaskets, a window in the drop edge of the lid is provided for extrusion of the gasket through the window in the event of excess pressure. The disadvantages of that solution are the same as those mentioned for the preceding device that implements an indexed gasket.
An indexing safety gasket adapted to the mounted in the lid of a pressure cooker to seal the lid and the pan of the pressure cooker comprises a fastening element on the gasket adapted to cooperate with a fastening element on the lid for indexing rotation of the gasket with rotation of the lid, and a periphery having at least one outer notch to enable the gasket to deform radially at the outer notch in the event of the pressure cooker becoming excessive. The gasket may have at least one outer notch comprising a curved regular cutout extending substantially over the full height of the gasket. The at least one outer notch may comprise at least two outer notches.
The fastening element on the gasket may comprise a male element and the fastening element on the lid may comprise a female element. In other embodiments, the fastening element on the lid comprises a male element and the fastening element on the gasket comprises a female element. The male element may be formed by a projection crimped to the lid and adapted to penetrate into the female element, which comprises an orifice.
The projection may be secured to a top face of the lid and the orifice may be formed in the gasket so that the orifice extends in a direction that is substantially perpendicular to the plane in which the gasket extends. The projection may be secured to a peripheral drop edge of the lid and the orifice may be formed in the gasket in a substantially radial direction. The male element may comprise an integral portion of the gasket and the female element may comprise an opening formed through the lid.
The male element may comprise a stud integral with the body of the gasket, on a top portion of the gasket and the stud may be adapted to penetrate in the opening of the lid.
In other embodiments, the male element comprises a stud integral with the body of the gasket and extending radially from a leading edge of the gasket and the stud is adapted to penetrate in the opening of the lid.
In another aspect of the invention, a pressure cooker comprises a pan, a lid and a gasket adapted to be mounted in the lid, the gasket comprising a fastening element on the gasket and adapted to cooperate with a fastening element on the lid for indexing rotation of the gasket with rotation of the lid, and a periphery having at least one outer notch to enable the gasket to deform radially at the outer notch in the event of the pressure inside the pressure cooker becoming excessive.
The lid preferably has a flow hole formed through the lid so that the gasket progressively uncovers the flow hole to enable air to leak out progressively from the flow hole when the gasket deforms radially. The at least one outer notch may comprise at least five outer notches.